The Devil's Advisor
by Prince Yarar
Summary: Cedric wasn't ready to move on, and Rin was feeling kind of lonely being a demon. The story of how the Hufflepuff Golden Boy rose to become (the current) Satan's most terrifying second in command. Anime/Manga fusion. No pairings except canon references.
1. Gehenna Days Arc: Chapter 1

**Dog Days are Over**

"I shouldn't be visiting graveyards this often."

With the moonlight shining down the place and the starry sky that accompanied it, the coal tars infesting the place were even more of an eyesore than usual. The King of Gehenna began to light his fire, idly scaring (or burning) the pests out of his way. He wasn't doing this out of boredom. More because of the frustration from ruling for 20 years and still having to deal with low ranking demons trying to assassinate him every breakfast. Or lunch. Or dinner. He wasn't very good at keeping track of time. Not that it was his fault. Gehenna wasn't exactly keen on being logical about Time and Space. A certain crook would have laughed jovially and made a reference of Wonderland, and how the current King was Alice Liddell.

The fact that the him of now would understood that reference made Rin shivered. He wasn't going to start wearing a dress and chasing white rabbits, thank you very much.

Although, that very same crook would also reminded him that 20 years were a very short time for demons if it wasn't for Rin literally stabbing him in the back before cutting his tail off.

The short demon frowned at the memory. He didn't regret it one bit. He just hated that even after death, Mephisto still rubbed on him the wrong way.

"There you are." With a grin, Rin jumped on top of one of the broken statues, standing on both of its wings and looking down at his prey. "Heeeeey! Why don't you pick on someone your _own _size!" And of course, his prey's prey was even taller and broader than Rin himself. But the demon got the idea. It was a pitiful Flesh Hound, compared to Rin himself, but he thought he could spar with it for a while. After all it wasn't like he could demand Kuro to play with him all the time. Especially now that it was the Cait Sith's naptime.

The Flesh Hound growled but a sniff of Rin's scent was enough to make it backed away and ran with tails between its leg. "Oh, come _on_!" How weird that despite he got assassinations attempt at almost every turns back at Gehenna that every other demons that were in Assiah were smart enough to escape. Rin jumped down from the statue. He wasn't about to chase it, too much effort.

"Ah…" Rin turned around at the Flesh Hound's prey. "T-thank you." The young looking ghost looked up from the ground, having been cornered by the demon dog previously. The Demon King almost winced at how _teenager _the ghost sounded. And from the coal tars surrounding this place, his death must be recent too.

"Heh. Don't sweat it, kid. You should just move on to avoid this kind of confrontation ever again." Rin gave a reassuring grin and an advice. Which he one hundred percent sure was going to work on cheering this kid up.

And of course, he was wrong. He could almost hear Bon saying that in deadpan.

"I can't!" The ghost screamed. "I have- I have to warn my family! You-Know-Who is back! I have to-" He began to wheeze, "W-why am I not in my house? I chose to be a ghost, didn't I? Why am I-"

"Whoa! Kid! Calm down!" Rin grabbed a hold of the ghost. Could dead people have panic attack? "Calm down…" This kid's death must be very traumatic. Despite his size the ghost was trying to curl and be as small as possible. "Hey, what's your name?"

"C-Cedric…."

"All right, Cedric. Come with me, it's not safe here." Neither was Gehenna. But with Rin protecting him, everything was going to be fine.

Cedric nodded, wiping his tears and looking far younger than he did earlier. "O-okay…"

Rin smiled encouragingly, helping the boy stood up. He pulled out the key that was hanging around his neck like a necklace from beneath his shirt. The boy looked at him curiously as he was twisting the key in empty air. When the door appeared, the shock on the boy ghost's face was priceless. Rin chuckled a bit. "Come on. I'll make you some tea." He gestured with his head as he opened the door, revealing a pristine kitchen on the other side. The surprise on Cedric's face didn't last long, and instead of confusion or fear, it was an expression of wonder plastered on his face.

"What kind of Charm is this?" The brunet asked as he stepped inside.

Rin shrugged casually, "It's just a key." He wasn't going to admit he had no idea how it worked. Or that he did but already forgotten it. "Sit." He pulled a chair for Cedric. The dead boy looked hesitant before experimentally touching the seat. His brows creased in obvious confusion.

"I thought I was dead…" Cedric murmured, taking his seat.

"You are." Rin served the chamomile tea to the ghost. "Believe me, I won't bring you here if you were alive."

Cedric stopped reaching for his cup midway. "I am? But then- how come I can touch- where _is _here anyway?"

"That." The shorter man pointed at Cedric, "Promise you won't freak out?" The ghost nodded warily. Rin looked skeptical but knew better than withholding information. "You are in Gehenna. Spirit World. Or as human calls it, Hell."

By now, his tea was completely forgotten. "Excuse me?"

"Aaaah, don't worry. Since I took over, the demons are more interested in trying to kill me than humans." Rin waved off Cedric's incredulousness.

Cedric, however, was still confused and very much incredulous. "...and you are?"

"You can call me Rin. 'Your Majesty' in front of anyone else not Kuro or Ukobach." Before Cedric could ask his next question (plural actually, he has several of them), there was a slight tremor, almost like an earthquake. "Speak of the devils." Rin snickered as if he just told the funniest joke ever.

"_RIN!_" The Cait Sith mewled his name as he charged through the large double door. Cedric seemed ready to run to escape the impact of a giant two tailed cat only for said cat to poof and decrease in size. Rin caught Kuro with his right hand and the little chef demon Ukobach that had been riding Kuro with his other, pulling them into an embrace. "_You are back!_"

"Yeah. I see you are already well rested." Rin said fondly.

"_Who's that?_" Kuro peered curiously at the human ghost.

"This is Cedric. He's… um… Cedric." Rin introduced his guest, a bit embarrassed to realize that he was in fact didn't know who exactly Cedric was.

Kuro frowned, "_You shouldn't be inviting strangers to your home, Rin…._"

"It's fine! He's a human ghost! He won't be able to do anything to me!" The King of Gehenna put down his two companions on the dining table. He turned around and saw Cedric's full cup. "You don't like chamomile?"

The ghost snapped out of it. He was a bit embarrassed to have stared at Rin. He had never seen a cat like that, and whatever the little pink figure was. "Oh. No, it's not that…." Cedric drummed his fingers on the table's surface. "I just don't feel thirsty…"

Rin had learned enough tact over the years not to bluntly say that it was because the boy was dead. "Ah…" He scratched the back of his head, "Well, what do you want to do then?" The man looked at Cedric expectantly.

Said dead teenager immediately answered, "I need to go back to Hogwarts." He said with determination, only to falter at the next sentence. "I- Even though Harry- I know Harry will warn them- but-"

"No." Rin cut him off. He didn't know what or where Hogwarts was. But he certainly wouldn't let a ghost haunt any place. "What you need to do is to move on. Accept the fact that you have died."

"If that's what you were going to tell me… then what's the point in asking me what I want?" He was still trying to wrap his mind around the fact that Cedric Diggory has died. It was all so surreal. This place was surreal.

Rin sighed. He could sense a headache coming. "If you want, I could always send you back to that place to be a Flesh Hound's midnight snack. How about that?"

Cedric tensed, "Please don't."

"Yeah. Thought so." The shorter man nodded. "You can stay here until you are ready to let go. Much safer than out in Assiah or anywhere in Gehenna without my protection."

"R-right." Cedric still didn't understand what Assiah and Gehenna were. He doubted they were really Hell. Or that Rin was its King. But the man was nice enough to let him stay, even if he was a bit strange. So why complain? "Thank you."

Rin looked caught off guard for a split second before beaming brightly. "You're welcome."

Cedric returned the smile with less intensity.

He guessed he won't be coming home anytime soon.

* * *

**Notes**: Crossposting this from AO3 just to see if I get more reviews here lol


	2. Gehenna Days Arc: Chapter 2

**Night or Day, No One Can Tell**

Cedric couldn't sleep. Not because he didn't want to but more because he didn't _need _to. After eating the Asian cuisine ("Japanese." The man corrected him. "Asian cuisines are more than just Chinese, got it?") that Rin cooked with the help of the pink sprite, Cedric realized he didn't feel satisfied, or even hungry in the first place. And yet he managed to gobble down the food simply because the exotic taste was out of this world. Rin then showed him his room, which was luxurious for a simple person like Cedric. The Asian man began chatting with his cat in that strange language of his again, which the cat always responded with mewls and surprisingly a hiss this time. It didn't sound Japanese or Chinese. But then again Cedric didn't know much about either languages.

The room was blue-themed. Ravenclaw, his mind supplied. Cho, his heart reminded. "You okay there, kid?" Rin frowned, obviously confused by the sudden choked noise the teenager just made.

"I'm fine. Thank you for your hospitality." Cedric smiled politely.

"Heh. You have more tact than I was at your age." Rin chuckled earnestly before he seemed to snap at Kuro again. "Whatever." The man reverted back to English. "Get some rest." was the last thing he said to Cedric before leaving him in that room.

And now here he was. Lying on a bed far too big to be slept on alone. Trying to rest his mind but his body didn't even feel the exhaustion that he should have felt by now. So that was it then. He was truly dead, if his physical needs stopped functioning like this.

The realization was horrifying.

He curled in a fetal position, trying to calm himself by arranging his memory up to this point. He was a ghost. And yet he could touch things and unable to pass through walls as if he was still a corporeal being. Ghosts weren't corporeal. Not even poltergeists, who could only affect their surrounding to a certain degree. Maybe it was because of this place? Gehenna? Hell?

Was Rin's claim true then?

Cedric bolt up from his sleeping position. A new determination was painted on his expression. He didn't even need a wink of rest, so why waste his time in this room? He needed to find a way back to Hogwarts, to make sure that Harry got back safely. The Hufflepuff took a deep breath, before opening the door and began sneaking out. Many said his House never break any rules. It was just because they were good enough to never get caught. And this time too, he wouldn't get caught.

He bit his lower lip. His eyes were darting, looking around the place and only caught sight of the thick curtains blocking the windows and the far too empty hallway. Not even a painting to decorate the walls, or a rug to cover the floor. It was going to make it hard for him to navigate where he was going, with no landmark to tell him where he was.

After mulling it over, Cedric decided he needed to make a map as he wandered. Going back inside the room, he began to search for parchments and quill. He didn't find any quill, but found out the little tube with pointy edge was filled with ink to write. As for parchments, he found several, but they were already written on on both sides in symbols that he could only guessed as Japanese. Disheartened but not giving up, he decided to draw the map on his sleeve.

With his preparation complete, Cedric stepped outside the room again. First of all, he needed to check which floor he was in. He remembered going two stairs up from the kitchen, so he would at least be at the third floor. He had a feeling that it was more than that, though. The ghost experimentally touched the thick and rough material of the curtain. It felt warm compared to his own hands, which definitely stayed cold after death. He grabbed the cloth to see through the window only to be stopped by a yell. "Don't!"

Cedric didn't have time to turn around when Kuro the cat bit his hand. "Ouch!" He let go of the curtain and at the same time Kuro let go of his hand, looking smug. The cat's expression reminded him of an animagus instead of a real cat. "Why?" Cedric hissed.

"Sorry, should have told you before. You aren't supposed to open the curtain." Rin arrived with a tray of food. "It's bad outside." As Rin approached closer the scent of the freshly cooked food hit the ghost's sense of smell. "I tried making European breakfast. Kinda interesting experience. Should try it more often." The man mumbled to himself as he put the tray down on the table in the bedroom. "Come on! Sit, I can't eat this all by myself!" Kuro meowed and Rin looked offended, "Shut up!" He huffed.

"I'm not hungry..." Cedric mumbled.

"No shit, you are a ghost." Rin cackled humorously before stopping himself with a cough, seemingly embarrassed by his inappropriate humor. "Sorry about that." He grinned sheepishly. "Have a seat anyway. There's nothing wrong with eating food just because they taste good."

"...okay." He hesitantly said. Cedric was seated across Rin. He put the writing tube on the table, eyeing the food with nostalgia. This was similar to Hogwarts' typical breakfast, just less fancy.

"Oh hey, that's my fountain pen! Where did you find it?" The shorter man asked. Cedric jolted in his seat, afraid that he was about to get found out. "It's fine! You can keep it! Thing's too fancy for my taste." Rin smiled.

"Thank you." Cedric almost sighed in relief.

"You are welcome. Now, dig in!"

He ended up eating Rin's cooking again, but with less vigor than before. His mind was too preoccupied with the thought of his family and friends to enjoy the meal.

And it seemed, he didn't hide it as well as he thought.

"You are zoning out." Rin pointed out. "What's wrong?"

Cedric was sure he only asked out of politeness. So he replied with an uneasy smile. "No. It's nothing. Just reminded of my friends and family."

"Kid." The dark haired man frowned. "The best thing for you right now is to accept your death and move on." He bit off a large chunk of meat pie with a single bite, gulping it down with an annoyed expression.

"...you are awfully accommodating for a King of hell." Cedric commented as he stabbed his food gently and repeatedly.

"THE King of Hell." Rin corrected. "And trust me. You _want _me to be accommodating to you." He snorted. "And stop playing with your food. Eat."

"It doesn't make sense…" The Hufflepuff put down his fork. "Ghosts are supposed to be intangible. Unable to eat. And I know I _am _dead because I don't _need _to eat." He took a deep breath, or rather, mimicking the action. "And I won't be able to move on once I'm a ghost, anyway…"

Rin observed Cedric. He was leaning his cheek on his palm as he hummed. "I knew it." He said. "You were a wizard." Cedric gave him a look. "Alright, since you're dead and that means you are under my jurisdiction, guess it's okay for me to tell you this." Rin straightened himself, looking deadly serious for once. "An imprint of the soul and a soul itself are two different things. Your wizard's ghosts aren't a real soul, they are an echo at best. Everyone needs to move on. Do you really think that a human, dead or not, can stay sane living for hundred years unchanging? If the ghosts you met are real spirits they would have gone malicious by now."

Cedric was stunned. The boy shook a bit at the revelation. He tried to stay calm and composed. It wasn't the time to cry. "Is that mean-" His voice croaked. "Is that mean that there might be an echo of me back at Hogwarts?"

"Did you _want _to leave an echo?" At Cedric's silence, Rin took that as a no. "Then no, I don't think there's another you hanging out with your loved ones. Beside, echoes were usually only made _after _a soul moved on."

The ghost nodded hesitantly.

Rin tried to reassure the boy once more, "Hey. If you aren't ready to move on, you can stay here for a while. But remember, I will have to give you up if you keep prolonging your stay."

Cedric nodded. He wasn't sure what the man meant by 'giving him up' or even to whom. The Hufflepuff ate his meal slowly, savoring the flavor a dead man shouldn't be able to taste.

Kuro kept eyeing Cedric's meal. He noticed of course. With a tired smile, the brunet gave up his meat, much to the two tailed cat's pleasure. It wasn't like he needed it.

"Oh yeah, speaking of which." Rin finished his meal. Cedric didn't realize until he heard Rin talking again. "Don't accept any food that wasn't from me. Not even from Ukobach or Kuro here."

"Why?" Cedric asked.

"Someone might disguised themselves as either of us- Shh, lemme finish." He stopped Cedric from asking. "In the case of meeting me and you aren't sure if it was me, ask for a blue fire." Rin opened his palm, and a blue fire burn slowly on his hand, surprising Cedric. "If they can't produce this fire, for… say, the next second." Rin put down his flame. He searched his pocket for something before putting it on the table. "Stab 'em." It was a short knife, engraved with symbols that Cedric had not even seen in Ancient Rune class. "A stab should be enough to give you a head start to run."

Cedric couldn't help but gape. "You want me to stab _people_?"

"Not people. Demons. And only if they disguised themselves because that obviously meant they are up to something nasty real quick." Rin leant on his chair, twirling the knife with ease. Seeing Cedric's already pale face continued to be drained from its color, Rin sighed. "It's Gehenna. Hell. You have to expect the worst from its residents. Kill or be killed is our principle of living here. And it _also_ applies to dead spirits." He pointed the knife at Cedric before putting it back on the table and shoving it toward Cedric. "Keep it close to you."

The Hufflepuff warily took the knife, which seemed to satisfy Rin.

"Good boy." The smile that was given to Cedric was that of relief. Rin stood up from his chair, "Help me clean this up, would ya? It'd be easier with an extra pair of hands." For a moment, Cedric wondered if Rin was like Professor Moody. Someone whose paranoia was tempered through experience.

If Rin truly was the King of Hell, then he wouldn't be surprised.


	3. Gehenna Days Arc: Chapter 3

**Method in Madness**

Days blended inside the castle. From what he gathered it seemed there was a huge time difference between Hell-or Gehenna, as Rin insisted- and his own world. He helped cleaning up the dishes since there was nothing else to do here, and quite frankly the monotonous and empty hallway could have bored him to death if he wasn't already dead.

...and now he made dead jokes about himself. Wonderful.

Cedric now spent most of his time in the library with Kuro keeping an eye on him. The dust there wasn't thick, as if it was recently abandoned. However, the large quantity of the shelves made it not an easy feat to clean them all. Sometimes Kuro would grow in size to help him reach the taller places. He'd like to think they had grown quite close over the time, even if Cedric only had one sided conversation with the cat demon.

"Are you three the only residences here?" Cedric asked as he rode Kuro up to the flying shelves. Kuro mewled and the ghost took that as a yes. "That sounds lonely. I mean, this place is so big…" They landed softly on the top shelf. It was almost-well, maybe just a little- like flying with a broomstick. He liked the feeling of air pressure brushing against his skin.

He climbed down from Kuro and began to clean the dust-and that sticky thing that he hoped wasn't blood- off of the surface. "You know, I used to go to a school that uses a castle like this." Cedric said wistfully. "It's always bustling with activity. Students chattering on the hallway, paintings moving and gossiping about pretty much everything…" He chuckled. "There's also the infamous Weasley Twins. Well, depending on who you talk to, you can left out the 'in' from famous." It was strange. He felt nostalgic and yet it didn't feel like it had been that long.

"You really shouldn't talk about them." A young voice said, making Cedric jumped slightly from his position.

"Wh-who?" Rin's advice rang in his mind, and his hand started reaching out to the knife that was given to him. Cedric's neck craned as he looked around the library. He couldn't find anyone. There was only a confused looking Kuro with him. "...that-that wasn't you? Was it?" the giant cat just mewled back at him.

Cedric gulped. He was sure it wasn't his imagination.

The dead boy loosened his grip on the knife and let his hand out of his pocket. If someone 'unfriendly' was here, Kuro would definitely notice, wouldn't he? Unless this wasn't _Kuro_. Cedric shook his head, chasing away the paranoia out of it. Although, maybe he should keep a bit of them. _Constant Vigilance! _as Professor Moody always said.

Kuro nudged his face a bit. He nuzzled with worry and licked Cedric's face.

The teenager laughed. "I'm fine! Just-just thinking a bit." He stroke behind the cat's ear. "Let's get back to the kitchen before dinner…" The kitchen was a familiar place for him. And safe too. Not to mention the tea there would help him calm down considerably.

Cedric climbed Kuro's back. "I'm ready." He said, followed by an excited mewl by Kuro before they leapt off to the kitchen.

* * *

_There was always a method to madness._

The head was rolling. It wasn't even a clean cut through the neck. It was a clean cut through the jaw.

_And the method of Gehenna's madness, was power._

Rin sighed a long suffering sigh. He was truly thankful for Mephisto's tutoring, else he'd be a headless chicken running around Hell instead of _running _it. "Trying to start a rebellion with-" He made an incredulous gesture toward the rather large group of demons. "-these? Really?" Not to mention that he had perfected his bitchface thanks to him. "You remember that I beat Lucifer and his other Princes, right? I mean, I know you guys aren't that smart but this just takes the cake."

The man relaxed his posture, aggravating his 'subjects'. He leaned on Kurikara as he lowered his guard. One stupid thing caught the bait and lunged, only to be burnt to crisp. Rin didn't bat an eye. He couldn't afford to.

Instead he sneered at the rebellion. "Continue what you are doing, _please_. I have no entertainment down here after all."

_Power, and cruelty._

"Are you sure about that?" A humanoid demon-the leader, Rin assessed- sneered back while still being surrounded by his minions.

"Huuuuuh?" Rin craned his neck, making that annoyed, tough anime guy sound that he liked to imitate.

"After all, you have that human-"

He didn't get the chance to finish his threat. Or maybe it was just a mere insult. Whatever his intention was, it was a stupid move to make, since it made Rin decided to obliterate them with a surge of blue fire.

The cave under the mountain was quiet once again. There was only one demon left standing, and not even the ashes of his enemies were left.

Rin exhaled. "You are not touching him." A useless threat, for there was no one who would hear.

* * *

"Welcome back." Cedric greeted. There was an edge in his tone, but Rin wasn't sure what kind.

"Rin! Welcome back!" Kuro purred, "How was the patrol?"

The second Satan shrugged. "Boring." He grabbed a cookie and took a bite. "You?"

"We cleaned the library earlier!" Kuro said in his usual cheerful manner, at the same time as Cedric replied with, "Are you three really the only ones here?"

"Huh?" The three demons turned their heads to the only human soul there.

"What do you mean?" Rin narrowed his eyes, "Did you open the curtain?"

"No." Cedric shook his head, "I heard someone when in the library…" Rin leaned forward, gesturing Cedric to go on. "It said, 'you really shouldn't talk about them'..."

"That was me!" Kuro gasped. "You can hear me, Cedric?"

"Wh-that's not possible!" Rin snapped at his familiar. "Only demons can he-" The dread began to build and trash in his gut. Slowly, he turned his head toward Cedric. "Ced…" He croaked, throat suddenly dried. "How long have you been here?"

"I'm… not sure? I don't exactly have anything to tell the time on me." The boy looked nervous, "Why?"

Rin turned to Ukobach instead of answering, "Quick! How long has Cedric been here?" The answer he received was not to his liking.

"Rin?" Cedric fidgeted, "Is it something bad?"

"You need to move on." For once, the usually composed Rin looked scared. "_Now_."

"Even if you tell me that, I don't know how!" The dead boy replied with frustration.

"Fuck! I'm so stupid! I shouldn't have let you stay here!" The man stood up from his seat and kicked his chair in a tantrum.

Cedric backed away a bit. "Why? What's wrong?"

"There is always a method in madness…" Rin mumbled, so low that Cedric could barely hear it. "Gehenna is corrupt, I shouldn't have let you stay…" He said with regret. "It's-it's corrupting you, Ced. Your soul might not be able to move on at all…"


End file.
